Former FBI Director James Comey wrote in a memo that President Donald Trump asked to end to the investigation of national security adviser Michael Flynn, according to a source familiar with the matter.

Writing the memo was "not out of character," especially if he was concerned about the legality or moral issues, according to a former Justice Department official.

The New York Times first reported news of the memo.

Comey was in the Oval Office briefing the president along with the vice president and attorney general on February 14, according to a source close to Comey who has a copy of the memo. After the briefing, Trump "asked Sessions and Pence to leave," the source told CNN.

“I hope you can see your way clear to letting this go, to letting Flynn go,” Trump reportedly said to Mr. Comey in the memo. “He is a good guy. I hope you can let this go.”

Comey was "concerned" that the president was trying to "stop the investigation," the source told CNN. "He wrote a number of memos, a great many if not all were about contacts with Trump -- particularly the ones that made him feel uneasy."

The source did not know how many memos Comey had written.

The source said that Comey hopes the president's threats about "tapes" of their conversations indicate there are actually recordings of their conversations.

"He would love to have them," the source said. "One of his reasons for writing these memos is the concern this couldn't be corroborated -- but that could be met if there are tapes."

The White House issued a statement denying Trump made such a request.

"While the President has repeatedly expressed his view that General Flynn is a decent man who served and protected our country, the President has never asked Mr. Comey or anyone else to end any investigation, including any investigation involving General Flynn," a White House official said in a statement. "The President has the utmost respect for our law enforcement agencies, and all investigations. This is not a truthful or accurate portrayal of the conversation between the President and Mr. Comey."

Chairman of House oversight panel Jason Chaffetz said they will seek copies of former FBI director memos saying "My subpoena pen ready."

.@GOPoversight is going to get the Comey memo, if it exists. I need to see it sooner rather than later. I have my subpoena pen ready.

A spokeswoman for House Speaker Paul Ryan showed support for Chaffetz's push.

"We need to have all the facts, and it is appropriate for the House Oversight Committee to request this memo," Ryan spokeswoman AshLee Strong said in a statement.

Rep. Adam Schiff, who is a ranking Democrat member of the House Intelligence Committee spoke not long after the report was published saying that "enough is enough" and added that "we need to get to the bottom of this."

Schiff also said "If necessary we should subpoena (tapes) of Comey conversation if they exist."

Sen. Lindsey Graham said that Comey should testify before his Senate panel about his discussions with Trump over Flynn.

Comey had already been invited to testify before the Senate intelligence committee Tuesday about his firing a week ago, but he declined the invitation.

"OK, well, he's got to come in and tell us why," Graham said. "We're not going to try somebody on a piece of paper."

Graham also said he would consider a special prosecutor if Comey's recounting of the meeting was accurate.

"If I thought there was inappropriate behavior by the president, sure," Graham said.

Top Senate Democrat Chuck Schumer said "history is watching" and "the country is being tested in unprecedented ways."

Schumer said in a brief, somber floor speech Tuesday that he was "shaken" by the report that Trump asked Comey "to shut down an active investigation into a close political associate."

Schumer has been urging Deputy Attorney General Rod Rosenstein to name a special counsel to investigate Russian interference into last year's campaign and ties between Russian and Trump associates, including Flynn.